by Joel Bagg, Forage Development Specialist & District Sales Manager, Quality Seeds Ltd
Forage crop growth and development has been delayed somewhat by cool and dry weather, but should advance quickly with forecasted rain and warmer temperatures.Cool weather favours the growth and development of grasses more than alfalfa. Typically, this results in a greater proportion of grass in alfalfa mixtures, with more advanced grass maturity relative to the alfalfa. Early maturing orchard grass varieties are close to heading in some parts of the province. Older, less healthy alfalfa stands are beginning to become yellow with dandelions. Some fields that were fall cut are seeing delayed growth that will likely result in reduced 1st-cut yields. Grass stands have responded very well to early applied nitrogen with significantly more growth. Most new seedings are in the ground under excellent conditions.
Weed Control In New Seedings
Many new seedings have emerged with some at the unifoliate stage. Control of broadleaf annual weeds is very important in successful stand establishment, especially in direct seedings. Watch new seedings closely for the growth stage and annual broadleaf weeds to determine the optimum time of spraying. The risk of injury to alfalfa seedlings is greatly increased when 2,4-DB application is made outside of the first- to the fourth-trifoliate stage window. Uneven emergence can make targeting this window challenging. Target the first-trifoliate stage, when weeds are smaller and easier to control. 2,4-DB can suppress legume growth for a period of 2 – 3 weeks and severe injury can occur under drought or high temperatures. Grower experience has been that injury to seedling alfalfa plants can be minimized when reducing the lowest labelled rate of 2,4-DB by 25%. A reduced rate may reduce the level of weed control. MCPA can be added to 2,4-DB where mustard is a problem. Refer to OMAFRA Publication 75, Guide To Weed Control. www.omafra.gov.on.ca/english/crops/pub75/pub75ch10.pdf
Figure 1 – Counting trifoliates to determine optimum time of spraying. This alfalfa seedling is at the 3rd-trifoliate stage. Also note the cotyledons and unifoliate leaf. (Photo credit – D Undersander, UW)
Keep On Eye On Marginal Stands
Marginal stands are sometimes left to reassess for plant health and yield potential after an early 1st-cut. Dig some plants and cut open the root and crown with a knife. Watch for crown and root rots, brownish disclouration, spongy texture, a lack of secondary roots and nodulation, and assymetrical crowns. As a general rule, at least 55 stems per square foot provide a maximum yield. The critical level of 40 stems per square foot or less will result in a 25% yield reduction and should be rotated. Stem count numbers assume no significant additional yield contribution from grasses. Refer to “Check Alfalfa Stands and Make A Plan” www.qualityseeds.ca/blog/11-check-alfalfa-stands-this-spring-and-make-a-plan
Managing the first round of rotational grazing is important to ensure good productivity of the pasture for the rest of the summer. Common mistakes are:
- turning livestock onto pasture either too early or too late, and
- not rotating quickly enough between paddocks.
Turning livestock out too early before there is adequate grass growth will stress the pasture, resulting in a reduced total carrying capacity over the season. Turn-out that is a week too early can cost 2 or 3 weeks of grazing by the fall. Turning out livestock too late can cause problems trying to keep up to the rapid spring growth phase. Excess spring flush pastures that cannot be grazed should be harvested as hay or haylage.
In continuous grazing systems, growth should be 4 - 6 inches before turnout, depending on the grass species and stocking rate. In rotational grazing systems, livestock can begin grazing earlier at 3 - 4 inches, but should be moved through the first rotation very quickly in order to keep up with the rapid spring growth. The faster the grass is growing, the faster the rotation. The most efficient forage height for a cow to graze is from 4 - 10 inches and 3 - 6 inches for sheep and horses.